The invention is based on a method for associating ignition signals with a reference cylinder in multiple-spark ignition systems of internal combustion engines having externally supplied ignition.
To make the performance of precise testing of the ignition system of internal combustion engines possible, synchronization of the ignition system test unit with a reference signal is required. In ignition systems having a distributor, the ignition at the reference cylinder is detected with the aid of a trigger signal pickup, which is connected by means of the ignition cable leading to the reference signal, and is passed on to the ignition system test unit for evaluation and synchronization.
This method is unsuitable for multiple-spark ignition systems, because there is no mechanical distributor. In such ignition systems, a number of double-spark ignition coils corresponding to half the number of cylinders is used; these coils have two separate high-voltage windings, or preferably one such winding, which then generates two high-voltage signals of unlike polarity. It is also possible, however, to assign one ignition coil to each spark plug, with two or more ignition coils generating ignition pulses simultaneously. Ignition takes place in only one cylinder in the working stroke, while in the other cylinders, the ignition sparks remain without effect. The actual ignition spark is called the primary spark, while the other ignition spark is called the supporting spark.
In such ignition systems, the association of the ignition signals with a reference cylinder with the aid of a trigger signal pickup connected to the ignition cable leading to the reference signal is ambiguous, because the pickup outputs a signal both for the primary spark and for the supporting spark. Unequivocal synchronization of the ignition system test unit with the ignition signals for the reference signal would thus not be possible.
German Patent 33 25 308 discloses an ignition signal adaptor for distributorless ignition systems of internal combustion engines with externally supplied ignition, in which the signals detected by trigger tongs clamped to the two ignition lines connected to a double-spark ignition coil are delivered to a synchronizing stage, at the output of which the pulse train of actual ignition pulses is output for either one or the other cylinder. Synchronization with the actual ignition pulses in the reference signal is effected by depressing a key, which causes the output signal to switch over from one pulse train to the other.